1. Field of the Invention
The present invention relates to a controller for an injection system with a plurality of fuel injectors, a common fuel supply line for the fuel injectors, and a high-pressure pump for supplying the common fuel supply line with fuel. The controller is particularly applicable to a common-rail injection system of a diesel engine.
The precise dosage of the injected fuel quantity plays an essential role with regard to subsequent combustion and the resulting exhaust gases in engine actuation. Due to production-related component variances of the fuel injectors and aging phenomena during engine operation, the same must be calibrated while the engine is running. This means that deviations or drifts in the actually injected fuel quantity must be detected, quantified, and compensated by a corresponding adaptation of the injector actuation.
2. Description of Related Art
The actuation of the fuel injectors usually is based on a map controller, which from a desired injection value, generates an actuation value for actuating the fuel injector with reference to a specified map. Usually, the map comprises characteristic curves which describe the control value in dependence on the desired injection value for several different pressures in the injection system. The maps or characteristic curves usually are stored in the controller in the form of tables, since the mostly relatively complex dependence of the control values on the desired injection values normally cannot be represented via a mathematical function.
With regard to the adaptation of the actuation of the fuel injectors, the usual procedure is to monitor the injection values during the ongoing engine operation and, when deviations from the desired injection values are detected, correspondingly adapt the map stored in the map controller.
It is known from German document DE 197 26 100 B4 to adapt the values within the map, which lie in an environment of the values for a fuel injection, which is to be used for the adaption of the map. The procedure, however, means a high expenditure, since a large number of values from the map permanently has to be corrected or adapted.
From German document DE 10 2008 051 820 A1 it is furthermore known to determine a quantity deviation of an actual injection quantity from a nominal injection quantity in operation of the fuel injector and with reference to this quantity deviation adapt a typical injection characteristic of the fuel injector to a nominal injection characteristic. The typical injection characteristic is shifted, rotated or adapted in its shape in at least one section. The typical injection characteristic thereby obtains a new shape or position, which comes close to the nominal injection characteristic. However, this procedure also means an extensive modification of the values for the characteristic curves. Furthermore, German document DE 10 2008 051 820 does not disclose a method of how a corresponding adaption of the typical characteristic curves can be performed efficiently.